As Nick explains in chapter one, he moved East in order to start a new job and to experience a new llifestyle. He had grown up in the Midwest, and he felt ready for a change. A big cause of his feeling a need for a change was the fact that he had just returned from fighting in World War I. As he explains:
I graduated from New Haven in 1915, just a quarter of a century after my father, and a little later I participated in that delayed Teutonic migration known as the Great War. I enjoyed the counter-raid so thoroughly that I came back restless. Instead of being the warm centre of the world, the Middle West now seemed like the ragged edge of the universe — so I decided to go East and learn the bond business.
Though his parents are not especially happy with his decision, his father agrees to finance him for a year. This income, of course, is in addition to anything he can earn at his work. As to why he chooses this particular type of work, he says:
Everybody I knew was in the bond business, so I supposed it could support one more single man.
Nick initially planned to live in New York City close to work, but "when a young man at the office suggested that (they) take a house together in a commuting town, it sounded like a great idea." In this way, he ends up living next to Gatsby in West Egg. The other man, however, ends up taking a job elsewhere, so Nick lives in his bungalow alone.